A proposed fuel cell casing mounted on a vehicle has a pressure release hole that is formed in a casing body and is covered with a cover member. For example, in a fuel cell casing disclosed in Japanese Patent Laid-Open Gazette No. 2002-367647, a cover member is stuck to a casing body by means of a double-sided adhesive tape to be openable by a force applied to the cover member under a preset level of inner pressure of the fuel cell casing. This arrangement releases the inner pressure of the fuel cell casing and thereby protects the fuel cell casing from damages.